1. Field of the Invention
The present invention relates to a method of producing glycidyl methacrylate (GMA) from an alkali metal salt of methacrylic acid (MAA) and epichlorohydrin (EpCH). GMA is useful as materials for weather-resistant paints and resins.
2. Description of the Prior Art
In one of the known methods of producing GMA, an alkali metal salt of MAA obtained from MAA and an alkali metal compound is allowed to react with EpCH thereby forming GMA (for example, GB 2025970A). In this method, an alkali metal chloride is by-produced in an amount equimolar with GMA. Therefore, water is added to the reaction product liquid to dissolve the by-produced salt, and the water phase is discharged as a waste water after a phase separation. However, in the production of GMA by such a method, the amount of solid matters which are insoluble in both the upper oil phase and the lower water phase is gradually increased during the operation for phase separation. The formed insoluble solid matters make the phase separation incomplete, to cause the loss of useful components because the useful components are discharged together with the aqueous solution of by-produced salt. More disadvantageously, the insoluble solid matters are also formed during the discharge of the aqueous solution of by-produced salt, during its storage and during its transfer, to impede the stable driving of production apparatus and stable production by causing the clogging of transfer pipes and the breakdown of pumps. In addition, the treatment of waste insoluble solid matters is cost-consuming to drastically reduce the cost-effectiveness of the production. Therefore, it has been intensely demanded to develop a method of producing GMA free from the formation of insoluble solid matters during the phase separation and its formation in the separated aqueous solution of by-produced salt.
JP-A-2003-238478 (corresponding to US 2005/0119498A1) discloses a method of producing metal salts of MAA with a reduced amount of water, in which an aqueous solution of an alkali metal salt, alkaline earth metal salt or zinc salt of MAA is heated under reduced pressure in the presence of a water-soluble polymerization inhibitor, to remove the water in the metal salt of MAA by distillation. However, the proposed method relates to the production of metal salt of MAA and the removal of water from the metal salt of MAA. The production of GMA by the reaction of a metal salt of MAA and EpCH, and the problems mentioned above in such a GMA production are not described or considered in the patent document.